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IINITED STATES il rrice.

PATE T THOMAS A. EDISON, OF MENLO PARK, NEW JERSEY, ASSIGNOR TO THEEDISON ELECTRIC LIGHT COMPANY, OF NEW YORK, N. Y.

PROCESS OF MAKING INCANDE SCENTS.

SPECIFICATION forming part of Letters Patent No. 263,145, dated August22, 1882.

Application filed April 26, 1881. (No model.)

. clare that the following is a full and exact description of the same.

In several prior applications for patents by me made are describedvarious methods of manufacturing from various materials the incandescingcarbon conductors for the electric lamps usedin my system. Such'carbons,though differingin materials and methods of manufacture, possessedcertain essential unitary or common propertiesviz., flexibility and highresistance. B omass, nder some circumstances, an excellent and desirablematerial to use for such purpose, and in an application numbered 27,191I. have described a method of utilizing it for the incandescingconductors of electric lamps. v

The object of this invention is to furnish another method for treatingcarbon, plumbago, and allied substances so that a very flexible,durable, and effective incandescing conductor of any desired resistancemay be readily and economically made from such materials. Where for thispurpose plumbago or graphitoidal silicon, boron, or zirconium are usedthe treatment is as follows: The material used is reduced to animpalpable powder, and a quantity thereofis placed in a metal boxsuffioien tly strong to withstand a high pressure. The box should have aperfectly smooth polished bottom, and edges or sides extending upwardlyso as to form a chamber about onesixteenth of an inch deep, or evenmore, if relatively quite thick sheets are desired. A die with smoothpolished face is used, fitting into this box, which is substantially amold, and may be so designated. The mold is filled with the pulverizedmaterial, the top thereof evened ed, and the die brought down thereonwith great pressure, for which purpose it is preferable to use ahydraulic press. The result is a sheet of homogeneous material whosedensity depends upon the pressure used, which may be varied to suit therequirements of special purposes.

If it is desired to increase the resistance of the resultant material,the preferable way is to incorporate with thematerial noted, beforepressure into sheets, a proportion of powdered carbon or charcoal. Thelarger the proportion of carbon or charcoal used the greater theresistance of the sheets of any given density.

As the density may be varied by varying the pressure used, and theresistance regulated by proportioniug the amounts of pulverized carbonor charcoal mingled with the basic material, it follows that bothdensity and resistance may be regulated to suit the varying requirementsof different systems of lamps.

While all kinds of carbon may be used, as a rule, the substances firstmentioned are the easiest of manipulation. If, however, it be desired touse carbons having little or no cohesionsuch as charcoal--it may be doneby mixing therewith afluid havingin solution ahydrocarbon, the menstruumbeing one that is readily evaporable, the resultant paste being dried,powdered, pressed, and treated with hydrocarbon vapor, as hereiuafternoted.

From the sheets before noted the conductors or horseshoes are to bestamped or out, and so that the enlarged ends for clamping are madehomogeneous with the body ofthe conductor. In such operation there is acertain percentage of loss or breakage. This percentage is materiallyreduced by treating the sheets with hydrocarbon while heated toincandescence, or at least to avery high heat. To this end the sheetsmay be placed in a closed flask or retort provided with means wherebyhydrocarbon vapor may be passed therethrough over and around the sheets,the flask or retort placed in a furnace, and the sheets brought up to avery high heat; or the material may be heated by electricalincandescence while in a hydrocarbon vapor, the result being that thematerial becomes tough and flexible.

Instead of the dry powdered material being placed in the mold, it may bemade into a paste or .dough with any readily-evaporable agent, and themold filled with the paste or dough and allowed to dry.

The mold may be of any desired size, and it may be of the configurationdesired for the loop or horseshoe, so as to form the same dircctly, orafter the sheets are formed the loops or horseshoes, or anydesir'ed.shape, may be cut or stamped out, and then treated with the hydrocarbon,asdescribed,instead of the sheets 5 being so treated before cutting orstamping; but the latter is preferable.

What I claim is- I ,The methodof manufacturing incandescing conductors,consisting in pressing the pow- 1o dered graphite or other material intosheets,

then heatingthe sheets in the presence of a hydrocarbon vapor, asdescribed, and then cutting or stamping the conductors therefrom,substantially as set forth.

This specification signed and witnessed this :5 19th day of April, 1881.

THOMAS A. EDISON. Witnesses:

BERNARD J. KELLY, SAMUEL INsULL.

